Khan Academy
Khan Academy: Find Missing Length When Given Area of a Triangle
Find the base or height of a triangle when given the other and the area. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
Shodor Education Foundation
Shodor Interactivate: Triangle Explorer
This applet gives you practice finding the area of a triangle. Great place for students to "discover" how you find the area of a triangle. Directions are just a click away. [Requires Java.]
CK-12 Foundation
Ck 12: Geometry: Area of Composite Shapes Involving Triangles
[Free Registration/Login may be required to access all resource tools.] In this lesson students find areas of combined figures involving triangles. Students examine guided notes, review guided practice, watch instructional videos and...
CK-12 Foundation
Ck 12: Geometry: Unknown Dimensions of Triangles Grade 6
[Free Registration/Login may be required to access all resource tools.] Find the unknown dimensions of a triangle given its area and another dimension.
Varsity Tutors
Varsity Tutors: Hotmath: Review: Area
Find a quick, concise explanation of area and the formulas for different shapes. An example is given to help you understand how find the area of a shape. The area formulas are listed for different types of shapes.
University of Illinois
University of Illinois: Calculation of Triangle Area
Discusses how to find the area of a triangle using Heron's formula and provides interactive examples and problems you can solve.
ClassFlow
Class Flow: Area of Polygons
[Free Registration/Login Required] This flipchart provides students with notes and practice with using formulas for finding the area of triangles and quadrilaterals.
Discovery Education
Discovery Education: Web Math: Find Out Things About a Right Triangle
Gives basic info about a right triangle. Also students can substitute values for sides or angles in order to find missing values. The method for solving is then explained.
University of Cambridge
University of Cambridge: Nrich: Adding Triangles
Sharpen your logic and geometry skills by finding the area of a triangle. Solution available.
ClassFlow
Class Flow: Surface Area
[Free Registration/Login Required] In this lesson students learn how to find surface area of rectangular and triangular solids.
Math Open Reference
Math Open Reference: Volume of a Triangular Prism
Use this interactive tool to find the volume of a triangular prism. Try different figures for the height and the dimensions of the triangular face to see how these affect the volume. An accompanying chart also presents five methods for...
CK-12 Foundation
Ck 12: Determination of Unknown Triangle Measures Given Area
[Free Registration/Login may be required to access all resource tools.] Looks at triangle problems where you are given the area and must use trigonometry to find unknown sides or angles.
Khan Academy
Khan Academy: Find Base and Height on a Triangle
Identify the height of a triangle when given the base. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
CK-12 Foundation
Ck 12: Interactive Geometry: 1.6 Area or Perimeter of Triangles/ Quadrilaterals
Explore finding and measuring perimeter of figures.
Illustrative Mathematics
Illustrative Mathematics: G C Mutually Tangent Circles
Three circles are mutually tangent. Students are asked to find the total area of the circles plus the area inside where they meet. Students will need to know how to calculate the area of a circle, a sector of a circle, and an equilateral...
Windstream
Ojk's Precalculus Study Page: Area of a Triangle
An introduction to finding the area of a triangle using the sine function. Includes several pictures and examples.
Other
Algebra Lab: Areas and Perimeters of Triangles and Special Quadrilaterals
Learn how to find the areas and perimeters of triangles and special quadrilaterals.
OER Commons
Oer Commons: Polygons
Seventh graders find the area of regular polygons, recalling what they already know about the area of geometric shapes and generalizing a formula for any regular polygon.
ClassFlow
Class Flow: Review of Area
[Free Registration/Login Required] This flipchart is a review of calculating the area of squares, rectangles, and triangles for fifth graders. It also includes problems that work backwards from the area to find missing dimensions. It...
Maths Challenge
Maths challenge.net: Maximum Square
A challenging proof like geometry of finding the square inscribed in a triangle.
CK-12 Foundation
Ck 12: Trigonometry: Heron's Formula
[Free Registration/Login may be required to access all resource tools.] Find the area of a triangle when all three sides are known.
Calculator Soup
Calculator Soup: Isosceles Triangles Calculator
Use this calculator to find the sides, perimeter, area, semiperimeter, and altitude of an isosceles triangle.
University of Cambridge
University of Cambridge: Nrich: Disappearing Square
This one page website explains how to find the area of a triangle with an interactive graphic. It then offers a challenge. The solution is available right at the website.
Calculator Soup
Calculator Soup: Right Triangles Calculator
Use this calculator to find the unknown angles in a right triangle using the Pythagorean Theorem. Once you know the sides you can calculate the perimeter, semiperimeter, area, and the altitudes.